Valve for metering fluid

Abstract

A valve for metering fluid has an electromagnet for actuating a valve needle controlling a metering opening. The electromagnet generates, upon current flow, a magnetic flux that proceeds via an outer pole, a hollow-cylindrical inner pole, an armature displaceable on an armature guidance region embodied on the valve needle, and a working air gap delimited by the armature and inner pole. Disposed fixedly on the valve needle is an entraining element that penetrates axially displaceably into an entraining element guidance region embodied in the inner pole and has a radial stop shoulder for the armature which delimits a take-up travel or pre-stroke travel. The entraining element is extended into an additional inner pole having a pole surface formed by the stop shoulder, and is embodied magnetically conductively and a magnetic flux between the armature and valve needle is suppressed by way of a magnetically nonconductive material.

What is claimed is: 
     
       1. A valve for metering fluid, comprising:
 a metering opening in communication with a fluid inflow; 
 a valve needle configured to control the metering opening; 
 a valve closing spring applying a closing force acting on the valve needle in a direction to close the metering opening; 
 a magnetically conductive entraining element disposed fixedly on the valve needle; and 
 an electromagnet configured to actuate the valve needle against the closing force of the valve closing spring to uncover the metering opening by generating, upon current flow, a magnetic flux path that proceeds via an outer pole, a hollow-cylindrical inner pole, an armature displaceable on an armature guidance region embodied on the valve needle, and a first air gap that is delimited by the armature and the inner pole such that a region of the air gap extends continuously from the armature to the inner pole without any solid matter in the region; 
 wherein:
 the entraining element penetrates axially displaceably into an entraining element guidance region embodied in the inner pole and includes a radial stop shoulder for the armature which delimits a take-up or pre-stroke travel distance of the armature; 
 with respect to an axial direction parallel to a longitudinal extension of the valve needle, the take-up or pre-stroke travel distance is smaller than the first air gap; and 
 a magnetic flux between the armature and the valve needle is suppressed by way of a magnetically nonconductive material. 
 
 
     
     
       2. The valve as recited in  claim 1 , wherein the valve needle is made, at least in a needle portion having the armature guidance region, from a magnetically nonconductive material, and the armature is made entirely from a magnetically conductive material. 
     
     
       3. The valve as recited in  claim 1 , wherein the valve needle is made, at least in a needle portion having the armature guidance region, from a magnetically conductive material, and the armature has an inner region, surrounding the valve needle, made from a magnetically nonconductive material and an outer region, gaplessly surrounding the inner region, made from a magnetically conductive material. 
     
     
       4. The valve as recited in  claim 3 , wherein the inner region of the armature is a straight truncated circular cone having an annular upper surface facing toward the entraining element and an annular base surface facing away from the entraining element, and the outer region, gaplessly surrounding the inner region, is a cylindrical ring having an inner ring wall proceeding in a truncated conical shape. 
     
     
       5. The valve as recited in  claim 4 , wherein an outside diameter of a top surface of the truncated circular cone is slightly larger than an outside diameter of the valve needle, and an outside diameter of the base surface of the truncated circular cone is slightly smaller than an outside diameter of the armature. 
     
     
       6. The valve as recited in  claim 3 , wherein the armature is manufactured as a two-component part. 
     
     
       7. The valve as recited in  claim 6 , wherein the inner pole is constituted by a hollow-cylindrical magnet core fastened in a valve housing, and the outer pole by a magnet cup, surrounding the valve housing in the region of the magnet core, having a magnetic return piece to the magnet core; and wherein the radial stop shoulder, embodied on the entraining element, for the armature has a shoulder width that extends from the valve needle to close to the inner wall of the magnet core. 
     
     
       8. The valve as recited in  claim 7 , wherein the valve closure spring, which braces on the one hand against the entraining element and on the other hand against an alignment piece fastened on the magnet core, is disposed in the magnet core. 
     
     
       9. The valve as recited in  claim 1 , wherein a take-up or pre-stroke travel of the armature, which is over the take-up or pre-stroke travel distance up to the stop shoulder on the entraining element, is defined by an armature stop that is fixedly disposed on the valve needle on the side of the armature facing away from the entraining element, and a pre-stroke spring that presses the armature against the armature stop. 
     
     
       10. The valve as recited in  claim 9 , wherein a spring cup that that loosely surrounds the valve needle is fixedly disposed on the armature, and the pre-stroke spring braces on the one hand against the armature stop and on the other hand against the spring cup. 
     
     
       11. A valve for metering fluid, comprising:
 a metering opening in communication with a fluid inflow; 
 a valve needle configured to control the metering opening; 
 a valve closing spring applying a closing force acting on the valve needle in a direction to close the metering opening; 
 a magnetically conductive entraining element disposed fixedly on the valve needle; and 
 an electromagnet configured to actuate the valve needle against the closing force of the valve closing spring to uncover the metering opening by generating, upon current flow, a magnetic flux path that proceeds via an outer pole, a hollow-cylindrical inner pole, an armature displaceable on an armature guidance region embodied on the valve needle, the entraining element, a first air gap delimited by the armature and the entraining element, and a second air gap delimited by the armature and the inner pole; 
 wherein:
 the magnetic flux path splits into:
 a first path from the armature to the entraining element through the first air gap, without passing through the inner pole; and 
 a second path that is independent of the first path and is from the armature to the inner pole through the second air gap without passing through the entraining element; and 
 
 the entraining element penetrates axially displaceably into an entraining element guidance region embodied in the inner pole and includes a radial stop shoulder for the armature which delimits the first air gap; 
 with respect to an axial direction parallel to a longitudinal extension of the valve needle, the first air gap is smaller than the second air gap; 
 the first air gap defines a distance of a take-up or pre-stroke travel of the armature; and 
 a magnetic flux between the armature and the valve needle is suppressed by way of a magnetically nonconductive material. 
 
 
     
     
       12. The valve as recited in  claim 11 , wherein:
 a radially exterior region of an exterior end face of the armature directly faces an end face of the inner pole in the axial direction, without interruption by the entraining element; and 
 a radially interior region of the exterior end face of the armature directly faces an end face of the radial stop shoulder of the entraining element without interruption by the inner pole. 
 
     
     
       13. The valve as recited in  claim 12 , wherein the valve is configured so that:
 in absence of the magnetic flux, the armature is in a rest position in which the first and second air gaps are present; and 
 the armature is configured to travel, in response to generation of the magnetic flux, from (a) the rest position to (b) an intermediate position in which the first air gap is completely closed, the second air gap is partially opened, and the radially interior region of the exterior end face of the armature abuts against the end face of the radial stop shoulder, and then on to (c) a valve open position in which the first and second air gaps are both completely closed, the radially interior region of the exterior end face of the armature abuts against the end face of the radial stop shoulder, and the radially exterior region of the exterior end face of the armature abuts against the end face of the inner pole. 
 
     
     
       14. The valve as recited in  claim 13 , wherein:
 the travel from the rest position to the intermediate position is the take-up or pre-stroke travel, during which the valve needle remains in a rest position against the metering opening; and 
 the travel from the intermediate position to the valve open position causes the valve needle to lift off the metering opening. 
 
     
     
       15. The valve as recited in  claim 11 , wherein the valve is configured so that:
 in absence of the magnetic flux, the armature is in a rest position in which the first and second air gaps are present; and 
 the armature is configured to travel, in response to generation of the magnetic flux, from the rest position to an intermediate position in which the first air gap is completely closed and the second air gap is partially opened and then on to a valve open position in which the first and second air gaps are both completely closed. 
 
     
     
       16. The valve as recited in  claim 15 , wherein:
 the travel from the rest position to the intermediate position is the take-up or pre-stroke travel, during which the valve needle remains in a rest position against the metering opening; and the travel from the intermediate position to the valve open position causes the valve needle to lift off the metering opening.